1. Field of the Invention
This invention relates to processes for imparting smooth-dry and flame retardancy to synthetic-cellulosic-blended fabrics.
2. Description of the Prior Art
Cellulose by itself or in blends with synthetic fibers does not possess either smooth-dry (DP) or flame retardant (FR) characteristics. In order for the cellulose component to acquire these properties, it must be given a chemical finish. In the case of smooth-dry prformance, this is achieved by crosslinking the cellulosic component using one of the well known cross-linking agents such as dimethylol dihydroxyethyleneurea.
It is well known that it is more difficult to make certain blended fabrics flame retardant than it is to make all-cellulosic fabrics flame retardant. Blended fabrics in this category are particularly those made from cellulose and polyester. Moreover, the degree of difficulty increases as the amount of polyester in the blend becomes larger. For this reason, a blend containing 50% polyester and 50% cellulose is difficult to make flame retardant.
In the case of flame retardancy, performance is achieved by applying finishes that add concentrations of compounds that contain elements which have been found to be effective in improving the fire resistance of cellulose. Two systems are frequently employed. One system is based on finishes that add a combination of phosphorus and nitrogen to the fabric while the second utilizes a combination of antimony and halogen.
In the case of phosphorus-nitrogen finishes, a well-known finish is the so-called THPOH-NH.sub.3 [tetrakis(hydroxymethyl)phosphonium hydroxide-ammonia] finish. In this case, the THPOH is padded onto the fabric, the fabric is dried and the fabric is treated with gaseous ammonia. Subsequently, the fabric is oxidized. Attempts to give this fabric a durable-press finish by application of a crosslinking agent are generally unsuccessful because the crosslinking agent is reactive with the free -N-H groups in the THPOH-NH.sub.3 polymer rather than the OH group of cellulose. Similarly, pretreatment of the fabric with crosslinking agent prior to FR finishing, generally renders the FR treatment ineffective.
The other systems utilized to make cellulose or its blends flame retardant are based upon the use of compounds containing antimony and halogen. Typically, the antimony is added to the blended fabric in the form of antimony oxide. The halogenated component is added either in the form of halogenated polymers or as in small discrete inert halogenated compounds such as decabromodiphenyl oxide. Both the antimony and small discrete halogenated compounds are retained on the blended fabrics by means of being trapped in the blended fabric by the use of added polymers in the finish. Polyacrylates are frequently used for this purpose. The high add-ons of polymers in this finish tends to lead to a stiff blended fabric.